Synthesis, spectroscopic characterization, and magnetic properties of a mixed-valence copper(I,II) acetato complex with triphenylphosphine. Crystal structure of hexa-µ-acetato-tetrakis(triphenylphosphine)tetracopper(I,II)

Abstract

Copper(II) acetate reacts with triphenylphosphine, in ethanol solution, in a manner depending on the concentration of Cu(O₂CMe)₂, the molar ratio of PPh₃ to Cu^II, and temperature, to form the copper(I) complex [Cu(O₂CMe)(PPh₃)_n](n= 2 or 3), the copper(II) complex [Cu₂(O₂CMe)₄(PPh₃)₂], and the mixed-valence copper(I,II) complex [Cu₄(O₂CMe)₆(PPh₃)₄]. The pale blue-green complex [Cu₄(O₂CMe)₆(PPh₃)₄] has been characterized by microanalysis, electronic, i.r., and e.s.r. spectra, and magnetic susceptibility measurements. The crystal and molecular structure of [Cu₄(O₂CMe)₆(PPh₃)₄] has been determined from X-ray diffractometer data by the heavy-atom method and refined by full-matrix least-squares methods to R= 0.0565 for 2 227 reflections. Crystals are triclinic, space group P, with a= 10.898(8), b= 12.850(4), c= 19.877(8)Å, α= 121.03(2), β= 90.14(5), γ= 117.98(4)°, and Z= 1. The crystal structure comprises centrosymmetrical molecules of [Cu₄(O₂CMe)₆(PPh₃)₄]. Each molecule consists of a Cu₂(O₂CMe)₄ dimeric unit in the axial positions to which two molecular Cu(O₂CMe)(PPh₃)₂ ligands are co-ordinated through the oxygen atom of each acetate group.